Known apparatus for treatment of such organic waste water are generally of the type including a treating tank, contactors disposed in the tank for causing micro-organisms to be carried thereon, and an air diffuser pipe placed at the bottom of the treating tank which is connected to a blower. Air is blown from the diffuser pipe into the treating tank to supply oxygen to micro-organisms carried on the contactors and produce a bubble current, so that the waste water in the treating tank is treated while being agitated by the bubble current.
With the bubble current alone, however, a satisfactory current of water will not develop which is sufficient to agitate the waste water. As such, no efficient dissolution of oxygen can be expected and, in addition, contactors are likely to be blocked off by sludge. With the prior art arrangement, therefore, it is impracticable to expect that waste water treatment can be satisfactorily carried out.